This invention relates to a process and an apparatus for electrostatic copying. More specifically, it relates to an electrostatic copying process which comprises a step of forming an electrostatic latent image corresponding to an original on a photosensitive member having a photoconductive layer and a developing step for rendering the latent image visible, and to an electrostatic copying apparatus for performing the electrostatic copying process.
Generally, electrostatic copying processes for forming a copied image corresponding to an original include a step of forming an electrostatic latent image corresponding to an original on a photosensitive member having a photoconductive layer, and a developing step for rendering the electrostatic latent image visible. The electrostatic latent image-forming step comprises a step of applying an electrostatic charge to the photosensitive member and a step of projecting the original image on the photosensitive member. The electrostatic latent image formed on the photosensitive member in the latent image-forming step is rendered visible by developing it either directly or after transferring it to a suitable material (latent image transfer). The developing step can be performed by various methods, but generally, it is performed by applying a fine powdery developer (toner) to the electrostatic latent image.
Research and development have recently been done on various aspects of these electrostatic copying processes, especially the electrostatic latent image-forming step and the developing step, and various improvements have been suggested. None of them, however, are entirely satisfactory, and various problems still exist which have to be solved to obtain images of better quality. In particular, the developing step performed by applying a fine powdery developer to the electrostatic latent image poses many problems which are described in detail below with reference to the accompanying drawings.
Extensive research and development have also been undertaken in recent years on the electrostatic copying apparatus for the performance of these electrostatic copying processes, and various improvements have been suggested. These apparatuses, however, have to be improved further to obtain better copied images, permit easier operation and maintenance, and to render them simpler in structure and lower in price.